diff -r fb201e383f1b -r da575186d492 Nominal/Ex/Datatypes.thy
--- a/Nominal/Ex/Datatypes.thy	Tue Feb 19 05:38:46 2013 +0000
+++ b/Nominal/Ex/Datatypes.thy	Tue Feb 19 06:58:14 2013 +0000
@@ -8,7 +8,8 @@
   atom_decl - example by John Matthews
 *)
 
-nominal_datatype 'a::fs Maybe = 
+
+nominal_datatype 'a Maybe = 
   Nothing 
 | Just 'a